At the risk of lowering the tone right away, here's something you might not have guessed Matt LeBlanc would do: he shaves his chest hair into symmetrical designer stubble with a special strimmer. "It's like a chainsaw," he laughs. "No, it's like a trimmer thing really." And not just his chest hair. "No, I manscape." He manscapes? In real life? LeBlanc glances down at his body and nods. "Sure, I manscape." But he would like to make it clear that he has an absolutely "normal-sized penis".

For myself, I would like to make it clear that this isn't typical conversational territory. It's just that a new series of Episodes is about to begin, in which LeBlanc plays an actor called Matt LeBlanc who has designer chest stubble and a gigantic penis. And so here we are in a Soho club, discussing which anatomical details are really his, and which ones belong to "Matt LeBlanc". I think this is what people mean when they say the show is very postmodern.

"Television has that weird thing," LeBlanc observes. "You see a character in a multitude of situations over so many years, and you can't help but think that that is who that guy must be." He knows what he's talking about, for after playing the part of a struggling actor called Joey Tribbiani in Friends for a decade, so fused were the two when the show ended in 2004 that LeBlanc went off to play Joey again, in a spin-off sitcom called ... Joey. That wasn't massively successful, so he took four years off – only to return last year in Episodes, playing the part of an actor called Matt LeBlanc who used to be Joey in Friends.

That makes Episodes sound both more confusing and less imaginative than it is. The comedy drama is a satire about US television, starring Tamsin Greig and Stephen Mangan as a British couple, Beverly and Sean, whose Bafta-winning sitcom is picked up by a monstrous LA network executive. Relocated to Hollywood to make an American version, the couple are horrified to see their original leading man promptly replaced by an actor called Matt LeBlanc, who used to be a huge star in Friends, but now desperately needs a new hit show to get his career back on track. This LeBlanc is wildly rich and rather cynical, quite arrogant but slightly lost, and manages to ruin both their pilot and their marriage – the former by being ludicrously ill-cast, the latter by carelessly sleeping with Beverly. Series one of Episodes ended with the calamitous news that their pilot is, inexplicably, a hit – locking the trio together in LA to make the show, and setting the scene for series two.

Episodes is co-written by one of the creators of Friends, David Crane, and his partner Jeffrey Klarik. I only wish they had written the not-so-great Joey as well, because Episodes is clever and funny and rude and surprising, and has LeBlanc back at his best. He only agreed to take the part because Crane has known him so long that he knew he could trust him – although he admits that that can be a double-edged sword. Occasionally the script has made him a tiny bit paranoid, trying to work out which bits of his character are comic hyperbole, and which might be more accurate than he would like to think.

"I was very sceptical and uncomfortable with the idea of playing myself, because I didn't understand what they were getting at. They said: 'Oh, well, we're not making a documentary; it's not you we're going to write.' I said: 'As long as it's not me – as long as it's a character that we can just slap my name on – and we can play with the guy. But I don't want it factual at all.' So what we came up with is the public's perception of Matt LeBlanc, the celebrity." What are the biggest differences between this character and the real him? "I can't answer that." Can't? "OK," he grins. "I can, but I won't."

He did ask for one or two plotlines to be taken out, but of course won't say which – "There were a couple of things that I just wasn't comfortable with." Because they were too close to his real life, or for fear viewers would think they were true when they weren't? "A little of both," he offers cagily. Did he worry about being made to look stupid? "No, I'm not worried about looking like a prick," he laughs, relaxing. "I am a prick!"

To prove it, he recalls the first day of filming. Having performed Friends and Joey in front of studio audiences, and then taken four years off, "The first take we do, as I'm going through it, I get to the first joke – and there's no laugh. And I charge through and get to the second joke, and the third joke, and the fourth joke; I get through the whole speech and there's not one laugh. And I'm like, 'Fuck, I don't know how to do this any more; I've completely fucked up.' And they yell 'Cut!', and everyone starts laughing. I was like, 'Oh, riii-ght, everyone's supposed to be quiet.' Yeah, I had a true Joey Tribbiani moment."

It's a generous anecdote, because LeBlanc has spent most of his adult life contending with everyone's assumption that he must be as lovably dim and Tiggerish as Joey. "People will speak slowly to me sometimes. And they always ask me if I'm all right, because I'm much more low-key and reserved than my character in Friends. They think that I'm depressed, or I'm sad, or upset – but I'm just not amped up to go out in front of an audience and do a TV show. That's not who I am."

LeBlanc in the new series of Episodes. Photograph: Hat Trick/BBC/Jack Barnes

In fact it's so far from who he is that for the first few minutes of the interview I panic that he's going to be hard work. He holds his shoulders almost rigidly stiff, and talks very seriously about the craft of comedy with an intelligence Joey certainly never displayed. "The majority of my background is multi-camera format, which is very broad and a very arch perception of reality. Whereas single camera tends to be more truthful and a little more intimate of a medium. Friends was an education in intelligent comedic banter; in intelligent vernacular. It was an education in scene study. It was an education in group dynamic. I came out of there with a masters degree in comedy."

But soon he starts to unwind and joke around. The scene in series one of Episodes when the network executive's wife makes a pass at him, sliding her hand down his trousers – "That was fun" – wasn't, he laughs, a million miles away from the kind of thing that would happen to him at the height of Friends' success. "No, that happened quite a bit. Well, not literally walk up and put their hand down my pants, no. But God, all kinds of strange things happened. I remember I was having lunch one day with David Schwimmer, early on – like season two or something – and we're sitting in this restaurant. This woman comes up and she has a baby – like a baby, not a toddler, a baby. And she goes: 'Oh my God, oh my God!' and practically throws the baby to David as she's digging in her purse for her camera. She doesn't hand the child to David and make sure that David's got her, so David goes: 'Oh, whoa – don't drop the baby.' But she just digs for the camera." That kind of thing must have been quite disturbing. "It was very disturbing," he agrees, deadpan. "She didn't even notice me. It sucked."

LeBlanc was only 26 when his world turned from being one that you or I would recognise, into one populated almost entirely by frantic hysterics. A small-town working-class carpenter from Massachusetts, the only child of a single mum, he had moved to New York at 17 when he realised he didn't want to spend his life hammering nails. He tried modelling, but at 5ft 11in wasn't tall enough for the catwalk, so he had a go at acting, but that didn't go too well either. When he auditioned for Friends he had just $11. By the end he was earning $1m an episode.

But by then, of course, he could barely leave his house, so I wonder if there was ever a moment when he had second thoughts about the appeal of success. "Well, yeah, that particular aspect of it. I still – well, that's like a constant elongated moment." It must have calmed down a bit by now, though, hasn't it?

"Yeah –ish. Justin Bieber is staying at my hotel right now, and there's throngs of young girls outside, and I came walking out and they didn't even fucking – couldn't care less. They were looking past me to see if he was there. I was like, 'Uh, hello?!'" But in truth he can never really leave Friends behind. "Because it's in re-runs so frequently all around the world, the show is now being discovered by a new generation of young people. So I've been stopped a few times by young girls and guys saying: 'Oh my God, you're that guy from … wow, you're so old! What happened to your hair? God!' That stings; that's not funny."

I don't think the comments really sting because at 44 he looks fantastic – and in fact, he was dyeing his hair throughout most of Friends. "I need, like, gallons of it every couple of weeks, but now I just can't afford to dye it any more," he jokes. He's certainly not as rich as the version of himself he plays in Episodes – "He's got his own jet! I don't have a jet. I would love to have a jet. I can't afford a jet." Then he admits: "Maybe a small jet. But who wants a small jet?"

He reluctantly concedes that he's rich enough never to have to work again, thanks not just to Friends but to Joey, which paid him a reported $15m per season. "I made a fucking shitload of money," he smiles, "so call it a failure all you want." But Joey was, nevertheless, widely considered a failure, so I wonder if with hindsight he wishes he'd never made the show. At the time he was divorcing Melissa Knight, a former model he married in 2003, and with whom he has an eight-year-old daughter, Marina. It wasn't the happiest chapter of his life.

"No, I would do that again; I thought that it was a good show. I just think that we were telling stories that emasculated the character. They wrote a guy who became very doubtful of himself in this new place, in Hollywood, no friends, can't meet girls – and that's not who Joey was. He was always, always, always, the consummate optimist. Always. And that's not who they wrote. That was very frustrating for me." He had begged Crane to write the script, but by then Crane was too burned out, and the studio didn't want to wait while the writer took some time off. "So, I guess if I could go back in time – to answer your question – I would have put my foot down and said: 'I'm not doing it without David.' That's the one thing I would do differently."

The comic premise behind Episodes is "LeBlanc's" fading career, and although the character is notionally fictional, didn't he worry that if this show had flopped too, the joke might not have seemed quite so funny? "Well, but if you really think about it," LeBlanc says cheerfully, "it really doesn't matter if it's not a success, because no one's going to fucking see it. So who gives a shit?"

I tell him I think that would only apply if nobody had heard of him before. "Yeah, but people have failed projects that go away quickly. I wasn't worried about that, because I know the writers so well – I knew I wouldn't be ashamed of the project. Whether it translated into ratings or not, that's out of my hands. But I knew that the show would be well written, and it would be something that I could be proud of, and that I could enjoy doing. And being the brunt of the joke – I don't really mind being the brunt of the joke if it's a good joke."

Happily the joke turned out to be more than good; LeBlanc won a Golden Globe for series one, and the rest of the cast give extremely funny performances – though what I took to be wildly exaggerated caricatures of TV people in LA really aren't, according to LeBlanc, that wide of the mark. "No, nope – and to preserve my career I'm not mentioning names – but, yeah, there's some absolutely fucking insane people in Hollywood. Insane. I know a few network guys that are like that. And the casting people that don't have a funny bone in their body, that are heads of comedy – yep. That said, there are some really, really talented, genuine, nice people. But they're not as interesting to write about as the fucking weirdos out there."

The LA weirdo count might explain why LeBlanc now spends at least half of his time on his cattle ranch in rural California, looking after his daughter. He loves being in London too – though all actors have to say that when interviewed here – but he says it is because people here don't mind quite extreme swearing. "You can say whatever you want all the time – and it's funny to hear it with an English accent; it doesn't sound so bad. It just is like, 'Aw, that sounds kind of sweet.' In America, no; it's absolutely not acceptable."

Disappointingly, it turns out that he's never listened to the Archers, in which Tamsin Greig plays Debbie Aldridge. "No, I'm afraid not – but she's just an absolute acting machine; she's so great. And a nice kisser, too; she told me I better not leave that out of interviews any more." The image of Joey and Debbie Aldridge kissing doesn't come naturally, but laughing, he explains: "What actually happened was, everyone had asked her in interviews what it was like to kiss me, and she said: 'I bet no one ever asks him what it's like to kiss me.' So, one interview – we were just doing round-table stuff – and someone said: 'What's it like to kiss Tamsin?' And I said, not thinking of the ramifications: 'Surprisingly sexy.' And she will never let me hear the end of it. So maybe I can redeem myself."